In the field of wireless communication receivers, different requirements relating to transceiver performance may be considered. One such requirement concerns so called phase discontinuity.
Phase discontinuity (PD) is a measure of change in phase between any two adjacent timeslots of an uplink transmission from a user equipment to a radio base station in a telecommunication system. Briefly, uplink (UL) relates typically relates to transmissions from the user equipment to the radio base station, while downlink (DL) typically relates to transmissions from the radio base station to the user equipment. The PD requirements for UL transmitted signals/channels are defined in High Speed Packet Access (HSPA) for single uplink (UL) antenna e.g. for UL Dedicated Physical Channel (DPCH), High Speed Dedicated Physical Control Channel (HS-DPCCH) and Enhanced Dedicated Channel (E-DCH).
For example, for the UL DPCH the rate of occurrence of any phase discontinuity on an uplink DPCH for the parameters specified in table 1 shall not exceed the values specified in table 2.
TABLE 1Parameters for Phase discontinuityParameterUnitLevelPower control step sizedB1
TABLE 2Phase discontinuity minimum requirementPhase discontinuityMaximum allowed rate ofΔθ in degreesoccurrence in HzΔθ ≦ 30150030 < Δθ ≦ 60300
Consider a known user equipment comprising a transmitter. For the purpose of explaining phase discontinuity, the transmitter includes two power amplifiers. Each of the two power amplifiers is operated when the transmission, to be transmitted, is at a transmit power in a respective transmit power range. When the user equipment switches from operating one power amplifier to operating the other power amplifier, the phase discontinuity occurs. In this context, the point in terms of e.g. power level at which the user equipment switches power amplifier may be referred to as a Power Amplifier (PA) switching point. In many scenarios, performance may be degraded and/or loss may increase when the user equipment switches between the two power amplifiers as described above.
Furthermore, in for example scenarios involving a multi antenna system such as Multiple-Input-Multiple-Output (MIMO), requirements relating to relative phase discontinuity may be applicable.
Consider another known user equipment capable of MIMO transmission. The user equipment comprises a transmitter as shown in FIG. 1. For the purpose of explaining relative phase discontinuity, the transmitter comprises two transmitter branches TX branch #1, TX branch #2.
Two absolute phases for transmitter branch #1 and #2, respectively, are denoted φ1(t) and φ2(t). A Relative Phase (RP) is defined as δφ(t)=φ1(t)−φ2(t). Then, the Relative Phase Discontinuity (RPD) is defined as a difference of RP between two time instants t1 and t2, i.e., δφ(t1)−δφ(t2). Thus, the relative phase discontinuity is a measure of change of relative phase between different transmitter branches for any two adjacent timeslots. Similarly to the phase discontinuity, the relative phase discontinuity may degrade performance and/or increase loss in many scenarios.